Method to solve particle performance of FSG layer by using UFU season film for FSG process

ABSTRACT

A method for reducing contaminants in a processing chamber  10  having chamber plasma processing region components comprising the following steps. The chamber plasma processing region components are cleaned. The chamber is then seasoned as follows. A first USG layer is formed over the chamber plasma processing region components. An FSG layer is formed over the first USG layer. A second USG layer is formed over the FSG layer. Wherein the USG, FSG, and second USG layers comprise a UFU season film. A UFU season film coating the chamber plasma processing region components of a processing chamber comprises: an inner USG layer over the chamber plasma processing region components; an FSG layer over the inner USG layer; and an outer USG layer over the FSG layer.

This is a division of patent application Ser. No. 09/747,135, now U. S.Pat. No. 6,479,098, filed date Dec. 26, 2000, Method To Solve ParticlePerformance Of FSG Layer By Using UFU Season Film for FSG Process,assigned to the same assignee as the present invention.

FIELD OF THE INVENTION

The present invention relates generally to fabrication of integratedcircuit devices and specifically to methods of cleaning/seasoningreaction chambers used in the processes to fabricate integrated circuitdevices.

BACKGROUND OF THE INVENTION

In high temperature plasma processes, such as high-density plasma (HDP),and chemical vapor deposition (CVD) processes, the likelihood thatundesirable mobile ion and metal contaminants will be driven out of thereaction chamber components increases. Therefore the chamber componentsand the exposed surface of the wafer chucks are seasoned, or coated, tominimize these undesirable mobile ion and metal contaminants and to alsoprotect these parts/surfaces during the necessary cleaning processes.

HDP-CVD Processing Chamber

FIG. 1 illustrates a cross-sectional view of a typical HDP-CVDprocessing chamber 10. Processing chamber 10 includes chamber body 12supporting dielectric dome 14 on its upper edge: Chamber body 12functions as an anode and may be composed of aluminum, for example.Inductive coil 16 insulated within insulative coil holder 18, ispositioned around dielectric dome 12 to provide an inductive plasmasource. Conducting, or semi-conducting; chamber lid 20 is supported onthe upper surface of dielectric dome 14 and functions as another anode.An electrostatic chuck 22 is positioned in the lower part of chamber 10and supports substrate 24 during processing. Insulative dielectricmaterial ring 26 surrounds the outer perimeter of chuck 22 to preventarcing between chuck 22 and the grounded chamber walls. Insulative ring26 may be comprised of a ceramic, for example.

Gases enter chamber 10 through gas inlets (not shown) positioned aroundthe perimeter of chamber body 12 and in chamber lid 20 above chuck 22.Chamber 10 is exhausted through exhaust passage 28 outward of the outeredge of chuck 22 by an exhaust pump (not shown). A throttle and gatevalve assembly control pressure within chamber 10 by controlling theexhaust of gases out of chamber 10.

An RF voltage is provided through inductive coil 16 (source RF) togenerate a high density plasma (HDP). The RF voltage applied to coil 16excite the gas introduced into chamber 10 into a plasma state.Additionally, an RF voltage may be coupled to chamber lid 20 to providea bias RF signal into chamber 10.

Depending upon the application, precursor gases may be introduced intochamber 10 to deposit a material onto substrate 24, or etch materialfrom substrate 24, to form integrated circuits (IC) on substrate 24.

Contaminant Material

Chamber lid 20, ceramic ring 26, dielectric dome 14, enclosure wall 12and gas inlets form part of the plasma processing region and are sourcesof contaminant material which may be volatilized into the gas phaseunder operating conditions within chamber 10, thereby contaminating theprocessing environment. For example mobile ions such as Na, Li and K,and metal particles such as Fe, Cr, Ar, Ni and Mg may be leached out ofchamber components 20, 26, 14, 12 when a capacitive or an inductiveplasma is struck in chamber 10. Such mobile ions and/or metal particles,when incorporated into the deposited films, compromise the structuralintegrity and electrical performance of the devices formed on substrate24. Also, deposits on chamber components 20, 26, 14, 12 can buildupafter a series of substrates 24 have been processed that can flake offand become another source of particles that can damage the circuits.

Chamber Cleaning/Seasoning

Such particle contamination within chamber 10 is controlled byperiodically cleaning chamber 10 using cleaning gases, usuallyfluorinated compounds and inductively and capacitively coupled plasmas.Once the chamber has been sufficiently cleaned of the process gases andthe cleaning by-products have been exhausted out of chamber 10, a seasonstep is performed to deposit a layer of material onto components 20, 26,14, 12 of chamber 10 forming the processing region to seal thecontaminants and reduce the contamination level during processing. Thecleaning step is typically carried out by depositing a film to coat theinterior surfaces forming the processing region.

Silane gas may be used to deposit a layer of silicon dioxide ontocomponents 20, 26, 14, 12:

SiH₄+O₂→SiO₂+2H₂

Silicon tetrafluoride may likewise be used to deposit a layer of siliconoxyfluoride:

SiF₄+O₂→SiO_(x)F_(y)

Other season films may also be used.

For example, U.S. Pat. No. 5,811,356 to Murugesh et al and U.S. Pat. No.6,020,035 to Gupta et al. describe seasoning processes involvingfluorinated silica glass (FSG) layers.

U.S. Pat. No. 6,060,397 to Seamons et al. and U.S. Pat. No. 6,014,979 toVan Autryve et al. describe seasoning processes.

U.S. Pat. No. 5,976,900 to Qiao et al. describes a method whereby aphosphorous and/or a boron coating film is used after cleaning.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to utilize asandwich USG/FSG/USG (UFU) chamber season film regimen for hightemperature chamber processing.

Another object of the present invention is to improve the particleperformance of the FSG season film.

A further object of the present invention is to increase the availabletime of HDP FSG CVD machine (M/C) result from particle down.

Yet another object of the present invention is to maintain a minimalstatistical deviation of fluorine concentration ([F]) within the FSGlayer of a UFU chamber season film.

Other Objects will Appear Hereinafter

It has now been discovered that the above and other objects of thepresent invention may be accomplished in the following manner.Specifically, the chamber plasma processing region components of aprocessing chamber are cleaned. The chamber is then seasoned as follows.A first USG layer is formed over the chamber plasma processing regioncomponents. An FSG layer is formed over the first USG layer. A secondUSG layer is formed over the FSG layer. Wherein the USG, FSG, and secondUSG layers comprise a UFU season film. A UFU season film coating thechamber plasma processing region components of a processing chambercomprises: an inner USG layer over the chamber plasma processing regioncomponents; an FSG layer over the inner USG layer; and an outer USGlayer over the FSG layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more clearly understood from the followingdescription taken in conjunction with the accompanying drawings in whichlike reference numerals designate similar or corresponding elements,regions and portions and in which:

FIG. 1 is a schematic view of an HDP-CVD process chamber.

FIG. 2 is a flow diagram illustrating the method of the presentinvention.

FIG. 3A is an enlarged view of the process chamber wall portion of FIG.1 designated “FIG. 3A” illustrating the formation of the UFU seasoningfilm in accordance with the present invention.

FIGS. 3B and 3C, with FIG. 3A, illustrate the preferred embodiment ofthe present invention.

FIG. 4 is a table comparison of the particle count for the STD CleanProcess (UF) known to the inventors and the present invention UFU SeasonFilm for 2× Clean (UFU).

FIG. 5 is a graph comparison of the particle count for the STD CleanProcess known to the inventors and the present invention UFU Season Filmfor 2× Clean.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Unless otherwise specified, all structures, layers, steps, methods, etc.may be formed or accomplished by conventional steps or methods known inthe prior art.

Accordingly, FIG. 2 is a flow chart of the method of the presentinvention. That is: (1) two production runs are conducted within chamber10 (i.e. two sets of wafers are processed within chamber 10); (2) thechamber plasma processing region components (20, 26, 14, 12 and the gasinlets (not shown)) are then cleaned; (3) a first undoped silica glass(USG) layer 30 is formed upon the cleaned chamber plasma processingregion components; (4) a thin doped fluorine silica glass (FSG) layer 32is formed upon the first USG layer; (5) a second USG layer 34 is thenformed upon the FSG layer 32 to complete formation of UFU season film50.

FIGS. 3A to 3C illustrate cross-sectional schematic views of thepreferred method in forming season film 50 in accordance with thepresent invention. It is noted that although only a portion of chamberbody 12 wall is specifically illustrated in FIGS. 3A to 3C, season film50 is formed on all of chamber plasma processing region components 20,26, 14, 12 and the gas inlets (not shown). FIG. 3A is an enlarged viewof the portion of FIG. 1 denoted as “FIG. 3A.”

The method of the present invention allows for two production runswithin chamber 10 before cleaning/seasoning steps are required. Aftertwo production runs, the chamber plasma processing region components(20, 26, 14, 12 and the gas inlets (not shown)) are cleaned by anappropriate process/method. The preferred chamber cleaning method usedif UFU season film for two production runs.

Formation of UFU Season Film 50

As shown in FIG. 3A, a first undoped silica glass (USG) layer 30,preferably having a thickness of from about 900 to 1100 Å, morepreferably from about 950 to 1050 Å, and most preferably about 1000 Å,is formed upon the cleaned chamber plasma processing region components(20, 26, 14, 12 and the gas inlets (not shown)) under the followingconditions:

Season - 1 about 20 seconds by time Ar-side about 95 sccm turbo about 50mT Ar-top about 15 sccm about 3500 W RF, about 1W side-RF O₂-side about270 sccm 0W OFF O₂-top about 20 sccm SiH₄-side about 180 sccm SiF₄ 0sccm

Thin doped fluorine oxide (fluorine silica glass (FSG)) season layer 32,preferably having a thickness from about 270 to 330 Å, more preferablyfrom about 285 to 315 Å, and most preferably about 300 Å, is them formedupon first USG layer 30 under the following conditions:

F Intro about 3 seconds by time Ar-side about 95 sccm turbo about 50 mTAr-top about 15 sccm about 3500 W RF, about 1W side-RF O₂-side about 270sccm 0W OFF O₂-top about 20 sccm SiH₄-side about 180 sccm SiF₄ about 5sccm F Purge about 3 seconds by time Ar-side about 95 sccm turbo about50 mT Ar-top about 15 sccm about 3500 W RF, about 1W side-RF O₂-sideabout 270 sccm 0W OFF O₂-top about 20 sccm SiH₄-side about 180 sccm SiF₄about 5 sccm

FSG layer 32 has a fluorine concentration ([F])) less than about 4% butgreater than the [F] of the wafer.

FSG layer 32 avoids fluorine deviation for fluorine concentration fromwafer to wafer because [F] is controlled by diffusion mechanism insteadof surface concentration limit. Furthermore, because the layer 34 isfluorine free, the diffusion and not the surface concentration controls.

Second USG layer 34, having a thickness of preferably from about 1350 to1650 Å, more preferably from about 1450 to 1550 Å, and most preferablyabout 1500 Å, is then formed upon FSG film 32 under the followingconditions:

Season - 2 about 32 seconds by time Ar-side about 95 sccm turbo about 50mT Ar-top about 15 sccm about 3500 W RF, about 1W side-RF O₂-side about270 sccm 0W OFF O₂-top about 20 sccm SiH₄-side about 180 sccm SiF₄ 0sccm

Second USG layer 34 seals the weakened surface of FSG layer 32, avoidingparticle source.

First USG layer 30/FSG layer 32/second USG layer 34 sandwich structurecomprise UFU season film 50.

Standard Clean Process—A Process Known to the Inventors

The standard clean process (STD Clean Process) (not shown) known to theinventors (not to be considered prior art) is a 1× clean process, i.e.the plasma processing region components are cleaned/seasoned after onlya single production run. Under the STD Clean Process a single USG layeris formed upon the cleaned chamber plasma processing region componentsunder the following conditions:

Season about 45 seconds by time Ar-side about 95 sccm turbo about 50 mTAr-top about 15 sccm about 3500 W RF, about 1W side-RF O₂-side about 270sccm 0W OFF O₂-top about 20 sccm SiH₄-side about 180 sccm SiF₄ 0 sccm

An FSG layer is then formed upon the single USG layer under thefollowing conditions:

F Intro about 3 seconds by time Ar-side about 95 sccm turbo about 50 mTAr-top about 15 sccm about 3500 W RF, about 1W side RF O₂-side about 270sccm 0W OFF O₂-top about 20 sccm SiH₄-side about 180 sccm SiF₄ about 5sccm F Purge about 3 seconds by time Ar-side about 95 sccm turbo about50 mT Ar-top about 15 sccm about 3500 W RF, about 1W side-RF O₂-sideabout 270 sccm 0W OFF O₂-top about 20 sccm SiH₄-side about 180 sccm SiF₄about 5 sccm

However, the STD Clean Process still has an unacceptable particle count(see below)

Particle Performance: Present Invention UFU 2× Season Versus STD CleanProcess

Wafer cassettes having wafers designated “Bare-0.2,” “FSG 8-6.5K,” and“FSG 8-6.5K” were sequentially loaded processed. One cassette of wafersdesignated as “FSG 8-6.5K” were processed under STD Clean Process andone cassette of wafers designated as “FSG 8-6.5K” were processed underthe present invention UFU Season Film for 2× Clean with the wafersdesignated as “Bare-0.2” not so processed:

STD Clean Process Particle Count (EA) UFU Season Film for 2X Clean TotalCount/Area Count Total Count/Area Count Bare-0.2 104/3  0/1 FSG 8-6.5K15/0  0/0 FSG 8-6.5K 4/1 1/0

Comparison of Particle Counts for STD Clean Process and UFU Season Filmfor 2× Clean

FIG. 4 is a chart comparison of the particle count for the STD CleanProcess (“UF”) known to the inventors and the present invention UFUSeason Film for 2× Clean (“UFU”) by KLA scan (in-line data). (KLA is akind of instrument for particle detection production wafer.)

As evidenced by the FIG. 4 chart, the particle count (EA) when utilizingthe UFU method of the present invention is markedly decreased forparticle sizes equal to or smaller than about 0.5 μm. That is: forparticle size<0.3 μm, the average EA for the UF split condition is 3while the average EA for the UFU split condition is but 0.333; and forparticle size from about 0.3 to 0.5 μm, the average EA for the UF splitcondition is 2 while the average EA for the UFU split condition is but0.2. The particle count (EA) is not improved for particle sizes largerthan about 0.5 μm when utilizing the UFU method of the presentinvention.

FIG. 5 is a graph comparison (special precise control (SPC) off-linedata) of the particle count for the STD Clean Process (STD CLN Process)known to the inventors and the present invention UFU Season Film for 2×Clean (UFU Season Structure). The SPC defines any control limits forproduction parameters, including particle.

Particle count (EA) is plotted versus wafer count (pieces) with the rawdata for two runs when the present invention is utilized is shown to theright of the graph. As is evident, the particle count when then theinstant UFU invention is greatly, and consistently reduced, compared tothe STD Clean Process as shown on the left side of the graph for pieces1, 2, 5, and 6, and when two runs utilizing the present are graphed tothe right of the STD Clean Process comparison for pieces 1, 2, 3, 7, 14,15, 16, 23, 24, and 25.

A further study of particle trend and total particle count by using theUFU season film 50 in accordance with the present invention as comparedto a UF season film presented the following results for three cases:

Average of UF Average of UFU 1. 12.2 10.5 2. 17.9 10.5 3. 18.8 9.7

[F] Concentration Variation

It has been found that the variation of fluorine concentration ([F])when using the UFU Season Film method of the present invention isacceptable as compared to no introduction of F in the season film, withF introduction in the exposed season film, and using the UFU Season Filmmethod (USG/FSG/USG) shown below:

No Fluorine With Fluorine introduction introduction UFU Season Film1^(st) w/f 3.99 4.17 4.42 2^(nd) w/f 4.23 4.19 4.46 Δ +0.24 +0.02 +0.04

The F deviation of +0.24 when no F is introduced is too great, while theF deviation when using the UFU season film 50 of the present inventionis acceptable as the F concentration is controlled by diffusionmechanism instead of surface concentration limit. The F concentrationrefers to the layer with fluorine introduction, which is the UF layer.

Advantages of the Present Invention

The advantages of the present invention include:

1. for particle count performance, the particle count (EA) coulddecrease 10 EA from 10 EA to 10EA for mean value of off-line SPC andin-line KLA data;

2. deviation of [F] is largely decreased by using UFU season film 50;and

3. the FSG machine (M/C) capacity is increased.

While particular embodiments of the present invention have beenillustrated and described, it is not intended to limit the invention,except as defined by the following claims.

We claim:
 1. A UFU season film coating the chamber plasma processingregion components of a processing chamber, comprising: an inner USGlayer over the chamber plasma processing region components; an FSG layerover the inner USG layer; and an outer USG layer over the FSG layer. 2.The article of claim 1, wherein the inner USG layer is from about 900 to1100 Å thick, the FSG layer is from about 270 to 330 Å thick, and theouter USG layer is from about 1350 to 1650 Å thick.
 3. The article ofclaim 1, wherein the inner USG layer is from about 950 to 1050 Å thick,the FSG layer is from about 285 to 315 Å thick, and the outer USG layeris from about 1450 to 1550 Å thick.
 4. The article of claim 1, whereinthe inner USG layer is about 1000 Å thick, the FSG layer is about 300 Åthick, and the outer USG layer is about 1500 Å thick.
 5. The article ofclaim 1, wherein the FSG layer has less than about 4% fluorine.
 6. A UFUseason film coating the chamber plasma processing region components of aprocessing chamber, comprising: an inner USG layer over the chamberplasma processing region components; the lower USG layer having athickness of from about 900 to 1100 Å; an FSG layer over the inner USGlayer 30; the FSG layer having a thickness of from about 270 to 330 Åand less than about 4% F; and an outer USG layer over the FSG layer; theouter USG layer having a thickness of from about 1350 to 1650 Å.
 7. Thearticle of claim 6, wherein the inner USG layer is from about 950 to1050 Å thick, the FSG layer is from about 285 to 315 Å thick, and theouter USG layer is from about 1450 to 1550 Å thick.
 8. The article ofclaim 6, wherein the inner USG layer is about 1000 Å thick, the FSGlayer is about 300 Å thick, and the outer USG layer is about 1500 Åthick.
 9. The article of claim 1, wherein the chamber plasma processingregion components are clean.
 10. The article of claim 6, wherein thechamber plasma processing region components are clean.